Sound absorbing materials are used to suppress various types of noise. For example, a sound absorbing material for a vehicle exterior is used to suppress vehicle exterior noise (moving car noise generated when traveling) that infiltrates the interior of the vehicle. Examples of documents serving as references in this field include Japanese Unexamined Patent Application Publication No. 2007-261359 and Japanese Unexamined Patent Application Publication No. 2009-184296.
In the Japanese Unexamined Patent Application Publication No. 2007-261359 is disclosed a sound absorbing material for a vehicle exterior having a nonwoven fabric comprising main fibers and binder fibers, wherein the nonwoven fabric is provided with a resin layer formed by heating a powdery resin provided on the surface of the nonwoven fabric, and the resin layer is porous with part of the powdery resin remaining in a particulate state.
In the Japanese Unexamined Patent Application Publication No. 2009-184296 is disclosed a sound absorbing material consisting of a composite nonwoven fabric formed by laminating and integrating an organic fiber nonwoven fabric (A) and a meltblown nonwoven fabric (B) consisting of organic fibers with a fineness of at most 0.5 dtex, wherein the organic fiber nonwoven fabric (A) consists of 10 to 90 wt. % of heat-bonding organic fibers (a) having a core-sheath structure with a fineness of 1.1 to 22 dtex and 10 to 90 wt. % of actually crimped-type polyester short fibers (b) having a fineness of 2.2 to 33 dtex, and the composite nonwoven fabric is formed by performing heat treatment with a dryer or by heated roll processing on the laminated organic fiber nonwoven fabric (A) and the meltblown nonwoven fabric (B) so as to melt the heat-bonding organic fibers (a) having a core-sheath structure so that the organic fiber nonwoven fabric (A) and the meltblown nonwoven fabric (B) are formed integrally.